The unloading tube on a combine harvester is comprised of a cylindrical housing, which encloses an auger. This tube is pivotally attached to the combine so as to allow it to swing out to a deployed operational position substantially normal to the direction of travel and extending upwardly for unloading, and swing into a more level, stowed position supported by its saddle, so as to extend rearwardly substantially parallel to the direction of travel the remainder of the time. The enclosed auger has helical flighting that when the auger is rotated causes grain to move generally longitudinally through the unloading tube. The discharge end of the tube is fitted with a discharge spout. As grain exits the spout, it falls to a separate vehicle for transport.
Typically the unloading tube has a discharge outlet in connection with the discharge spout and an associated dribble door biased toward a closed position partially covering the discharge outlet. During operation of the auger, if present in sufficient quantity, the grain will be pushed by the auger against the dribble door to push the door open. However, when only a small amount of grain is present, which is inadequate to force the door open, this grain will only press against the closed door.
A problem that can arise with usage of a spring loaded dribble door is that this grain remaining in the unloading tube is susceptible to discharge and loss at inappropriate times. For instance, the grain can slosh out over the top of the door, or it can force the door open, such as when the unloading tube is in the more level stowed position even with the auger not operating. This can occur, for instance as a result of a sudden acceleration of the combine or when traversing rough terrain, ditches and the like, and can leave a quantity or strip of grain on the ground.
Another problem that can occur when using a spring loaded dribble door is that, by design, the spring will oppose the opening of the door and the discharge of grain. When smaller or irregular amounts of grain are conveyed by the auger towards the door, the door may only partially open or possibly open by varying amounts as the amount of grain varies. The resulting discharge stream may be irregular and/or varied as influenced by the quantity of grain present making it susceptible to wind drift, which can be generally defined as sideward movement of elements of the downward flow of grain resulting from forces exerted by wind thereagainst. Even small amounts of wind drift can be significant because the grain is often unloaded while the combine is moving while the receiving vehicle is being driven or towed in parallel with the combine over rough terrain or furrows making steering difficult. In instances such as environments such as the plains region of North America, winds can be quite strong and gusty. Often the operator of the receiving vehicle may attempt to position one side or the other of the receiving vehicle more beneath the spout such that, with wind drift, the stream of grain will be directed more to the center of the receiving vehicle. This is facilitated by a tighter, more cohesive discharge stream of grain.
Reference in this regard, Reimer et al., U.S. Pat. No. 6,691,861, which discloses an auger discharge chute with a spring loaded dribble door that has been observed to suffer from at least some of the above problems. The Reimer discharge chute has a dribble door attached to the unloading tube discharge end by a hinge with a spring that biases the door to the upward or closed position. The force of the grain pushes and holds the door open during discharge operations. However, if the amount of grain being conveyed is varied or reduced, for instance, as the grain tank of the combine nears empty, the force generated by the grain against the door may be insufficient to hold the door fully open. This may result in the situation discussed above, such that the grain flow stream is influenced by the position of the door as well as the amount of grain present. Here, using a spring having sufficient force to reduce the amount of grain dribbling out when the auger is not operating, is disadvantageous. To counter the negative effects of the spring loaded door varying in position as a function of the spring force and the amount of grain present, the Reimer door is illustrated to be shortened and shaped as a spout which will likely facilitate grain flow thereover, but the variable position of the door will still have an influence on the flow path of the stream of grain, and additionally the shortened door means that the discharge outlet is not fully covered when the door is in a closed position, such that small amounts of grain can remain in the discharge outlet region of the tube and can urge the door open at inappropriate times as discussed above. Thus, when fully open, the Reimer dribble door may mating engage the chute and be removed from the flow of grain, but in any other position, the door may remain within the grain flow an influences the position, flow path, and other characteristics of the stream of grain.
In addition, it appears from FIGS. 1 and 4 of the Reimer patent that when the unloading door is open, it creates a V shaped groove in which grain can become lodged which may prevent the door from closing properly risking unintentional grain loss.
As another observed shortcoming of some known unloading tube constructions, they may include support ribs or struts which extend through the internal passage of the unloading tube from the wall of the unloading tube transversely through the grain flow region to the endmost bearing supporting the auger, which ribs or struts may be positioned, oriented, and/or of sufficiently large sectional extent perpendicular to the direction of grain flow so as to have the effect of obstructing, splitting or dividing the grain flow to such an extent as to disrupt or split the stream of grain exiting from the discharge outlet, so as to be less cohesive, and thus more susceptible to wind drift and other problems.
Therefore what is sought is a discharge door arrangement for an unloading tube that overcomes one or more of the problems set forth above, including more positive operation to facilitate emptying of grain from the tube, and holding the door closed when the unloading tube is not in use. The arrangement can further include struts supporting the endmost auger bearing oriented to be only minimally obstructive such that a more cohesive stream of grain can be directed to the transport vehicle.